1. Field of the Invention
The present invention relates to a bearing device such as a hub unit for a vehicle comprising a shaft and a bearing and a rolling bearing mounted to the shaft body.
2. Description of the Related Art
Referring to FIG. 7, in a conventional hub unit, a double row angular contact ball bearing 82 with vertex of contact angles outside of bearing is fitted and mounted around a shaft portion 81 of a hub wheel 80. A free end of the shaft portion 81 is bent outward in a radial direction by rolling-caulking. The bent caulked portion 85 pushes an outer end face of an inner ring 84 of the bearing 82. With this pushing operation, the bearing 82 is fixed to the hub wheel 80 to prevent the bearing 82 from falling out from the hub wheel 80.
Before the free end of the shaft portion 81 is caulked, the free end has a shape of a cylindrical portion. This cylindrical portion is rolling-caulked using a caulking jig. With this operation, the cylindrical portion of the shaft portion 81 is bent outward in the radial direction to form the caulked portion 85 so that the inner ring 84 is prevented from falling out.
In such a hub unit, an entire outer surface of the inner ring 84 of the bearing 82 is subjected to hardening treatment. Therefore, in order to enhance a resisting force against the falling-out phenomenon of the bearing 82, it is necessary to set a caulking load stronger.
On the other hand, if the caulking load is excessively strong, a raceway surface of the inner ring 84 is affected and there is an adverse possibility that rolling characteristics of the bearing 82 is deteriorated. Therefore, it is necessary to set the caulking load appropriately.